Women exposed to hairspray in the workplace in the early stages of pregnancy are more than twice as likely to give birth to a boy with a particular genital defect than other women, research has shown.
Hypospadias, which causes the urinary opening to be shifted beneath the penis, normally affects around one in 250 boys in the UK.
Although it can be corrected by surgery before a boy's first birthday, more severe cases can lead to urinary, sexual and fertility problems.
The link between the condition and high levels of exposure to hairspray was established by researchers led by Professor Paul Elliott from Imperial College London.
Hormone-disrupting hairspray chemicals called phthalates can affect reproductive development, and the increased risk was only seen in women whose jobs led to high exposure to hairspray chemicals, such as hairdressers, beauty therapists, research chemists and factory workers.
However, the same study showed that taking folic acid reduces the risk of giving birth to a child with the condition by 36%.
Professor Elliott said: "It is encouraging that our study showed that taking folic acid supplements in pregnancy may reduce the risk of a child being born with the condition.
"Further research is needed to understand better why women exposed to hairspray at work in the first three months of pregnancy may have increased risk of giving birth to a boy with hypospadias."